Republican presidential candidate Donald Trump speaks at a campaign rally, Oct. 18, 2016.
Republican presidential candidate Donald Trump speaks at a campaign rally, Oct. 18, 2016.

Republican presidential candidate Donald Trump has proposed instituting term limits on members of Congress as part of a multi-pronged package he says will clean up American politics.

"The time for congressional term limits has finally arrived," he told supporters Tuesday in the western state of Colorado.  "Not only will it end our government corruption, but we will end the economic stagnation that we're in right now."

U.S. presidents are constitutionally limited to two terms in office.  There is no such limit on members of the House of Representatives or the Senate, many of whom stay in office for repeated terms.  In the 2012 election, more than 90 percent of incumbents won re-election.

Trump's other proposed reforms include banning former members of Congress, their staff, and those who served in the executive branch of government from working as lobbyists for five years, and instituting lifetime bans on foreign lobbyists raising money for U.S. election candidates.

President Barack Obama on Tuesday criticized Trump's praise for Russian leader Vladimir Putin, saying his "continued flattery" is "unprecedented in American politics.

Trump has said he views a better U.S. relationship with Russia as an opportunity for the two countries to fight as partners against the Islamic State group.  He suggested this week that if he wins the November 8 election, he might visit Moscow even before being sworn in as president.

A spokesman for his opponent, Democrat Hillary Clinton, criticized those comments along with others Trump has made during the campaign.

"It's unclear why Donald Trump needs to meet with Vladimir Putin on November 9th since he's already repeating all his talking points, pushing his policy agenda and taking advantage of his espionage operation," said senior spokesman Glen Caplin.  "Rest assured that as president, Hillary Clinton will stand up to Putin in the face of his unacceptable behavior, not coddle him."

Russian President Vladimir Putin speaks to Russian
FILE - Russian President Vladimir Putin speaks to Russian journalists during a news conference following the BRICS summit in Goa, India, Oct. 16, 2016.

Clinton did not make any public appearances Tuesday ahead of Wednesday night's third and final debate between her and Trump.

During the previous two debates, each invited guests with the apparent aim of unnerving their opponent, including Trump inviting a group of women who accuse Clinton's husband, former President Bill Clinton, of sexually assaulting them.

Wednesday's guest list includes Trump's invitation of Obama's half brother Malik, who has said he will be voting for Trump.  Malik, a U.S. citizen, is three years older than the president, with whom he shares the same father.  The two men were once close, with Malik serving as best man at the president's wedding, but they have drifted apart in recent years.  Malik Obama also criticized some decisions by his brother and former Secretary of State Hillary Clinton, especially the move to oust former Libyan leader Moammar Gadhafi in 2011.

Clinton has invited billionaire Mark Cuban, who has sharply criticized Trump, as well as Hewlett-Packard CEO Meg Whitman.

The guests are seated in audiences that have in each of the previous debates been asked by moderators to not react to what the candidates say with any applause, cheering or boos.

An average of major political polls from the past two weeks indicated Clinton leading Trump by about seven points.

That advantage has spurred Clinton to expand her efforts into states that Republican candidates usually win, both as a move to help her own chance in the election and in a bid to boost the chances of more Democrats retaining or winning seats in Congress.

Democratic presidential candidate Hillary Clinton
Democratic presidential candidate Hillary Clinton boards her campaign plane at Westchester County Airport in White Plains, N.Y., Oct. 18, 2016, to travel to Las Vegas for the third presidential debate.

Clinton's campaign said it will spend $2 million more on advertising in the southwestern state of Arizona, which has been won by a Democratic presidential candidate only once in the past 16 elections.

It also plans to send one of it most popular surrogates, first lady Michelle Obama, to the state on Thursday to hold a rally for Clinton.  Recent polls indicate Clinton and Trump locked in a tight race in the state, located just along the border with Mexico.

In addition, the Clinton campaign is also increasing its efforts in Missouri and Indiana, two Midwestern states where Trump leads.  But both states have closely contested Senate races that Democrats and Republicans view as important in their efforts to win political control next year in the Senate, where Republicans now have a majority.

Trump told supporters Tuesday he does not believe the poll results and furthered his warnings of election fraud.

"They even want to try and rig the election at the polling booths where so many cities are corrupt and voter fraud is all too common," Trump said.

He also renewed his attacks on media outlets, which he has said throughout his run for president are treating him unfairly.

"Now, there's a voter fraud also with the media because they so poison the mind of the people by writing false stories," Trump said.

Trump has produced no evidence of voter fraud or other claims he has made, like alleging that Hillary Clinton was on drugs during their debate earlier this month.

There is scant evidence of vote fraud in United States elections, with one study saying there were only 31 instances of voter impersonation from 2000 to 2014, a period in which one billion votes were cast in a long list of elections.

FILE - Voters line up at a polling station to vot
FILE - Voters line up at a polling station to vote in Florida's presidential primary in Coral Gables, Florida. A survey by the political website Politico and the polling company Morning Consult suggested many Americans are skeptical about the integrity of the national election.

A survey by the political website Politico and the polling company Morning Consult suggested many Americans are skeptical about the integrity of the national election, with 41 percent of voters believing that the election could be "stolen" from Trump.  There was a wide partisan split in the poll results, with 73 percent of Republicans, but only 17 percent of Democrats, agreeing that there could be massive vote fraud.

President Obama said Tuesday that Trump should "stop whining" and instead focus on convincing voters to support him in next month's election.

"I have never seen in my lifetime or in modern political history any presidential candidate trying to discredit the elections and the election process before votes have even taken place," Obama said at a White House news conference alongside the visiting prime minister of Italy.  "It's unprecedented.  It happens to be based on no facts."

Trump's claims of vote fraud involve both the early voting that has been going on for the past few weeks as well as claims there will be further problems on election day that would lead to Clinton being unduly declared the winner.

Obama said that no matter the outcome, he expects the result of the vote to be honored.

"If he got the most votes, it would be my expectation of Hillary Clinton to offer a gracious concession speech and pledge to work with him in order to make sure that the American people benefit from an effective government," he said.

"And it would be my job to welcome Mr. Trump, regardless of what he's said about me, or my differences with him or my opinions, and escort him over to the Capitol [on inauguration day in January] in which there would be a peaceful transfer of power," the president added.  "That's what Americans do."

Obama was elected in 2008 and is finishing the second of his maximum two terms.  He will turn over the White House to his elected successor about 10 weeks after the election.

Obama and Vice President Joe Biden have appeared at campaign events in support of Clinton, who served as secretary of state during the first term of their administration.