Voters in Pennsylvania head to the polls Tuesday in a special congressional election with national implications for President Donald Trump and opposition Democrats.
The election is taking place in a congressional district that Trump won by 19 points in 2016, but where Democrats now hope for an upset that could be a preview of the midterm congressional elections in November.
The race pits Democrat Conor Lamb against Republican Rick Saccone. Saccone got some high-profile help on Saturday when Trump spoke on his behalf at a rally in Moon Township, Pennsylvania.
"We need him. We need Republicans. We need the votes. Otherwise, they are going to take away your tax cuts. They are going to take away your Second Amendment rights," Trump warned the crowd.
Key Test in Trumpland
Though Trump easily won the district in 2016, Lamb appears to be competitive in part because he is a moderate-to-conservative Democrat who personally opposes abortion and any new gun control measures. Lamb is hoping to pull off an upset with help from former Vice President Joe Biden.
"Passion and commitment rules in politics. Passion and commitment generates grass-roots support," Biden told a recent Lamb rally.
Republicans have poured money into the race, including millions of dollars in television advertisements in the final days before the election. Trump is trying to help Republicans avoid another setback on the way to the November midterm elections, where Democrats are favored to make gains.
In making his pitch to voters this election year, the president remains focused on his tax cut bill, new tariffs on steel and aluminum, and a diplomatic opening to North Korea.
But Trump remains stuck at about 40 percent approval in the polls, historically low for a second-year president, and a potential drag for Republican candidates in November.
"He's doing nothing to expand his base," said Jim Kessler of Third Way, a centrist Democrat advocacy group. "And also, political damage is kind of like sunburn. You don't really notice it as it is happening. And later in the day you realize, 'I'm red. I was out in the sun too long!' So, this takes a long period of time."
A Democratic victory Tuesday would send shock waves through the Republican Party, as Republicans have won the previous eight elections in the 18th Congressional District by a margin of at least 15 points. The seat became vacant late last year after the resignation of Republican Representative Tim Murphy.
The University of Virginia's Center for Politics now rates the contest a "toss-up," and several polls show Saccone and Lamb within a few points of one another. A new Monmouth University poll has Lamb ahead of Saccone by 51 to 45 percent, in one of the last surveys before the balloting. Last month, Saccone led in the same poll by a margin of 49 to 46 percent.
The Pennsylvania race will be seen by some as a test of Trump's popularity in an area he handily won in 2016. Conservative analyst Michael Barone of the American Enterprise Institute said for the most part, Trump's core supporters are sticking with him, despite an array of political distractions for the White House.
"The interesting thing about all this turmoil is, it is not changing too many people's votes," Barone said. "You've still got roughly a constituency of a large minority of Americans favoring Donald Trump and most of his policies, even as they change, sometimes from day to day."
The outcome of Tuesday's election should serve as the latest indicator of which party has the political momentum this election year — the president's Republican supporters or his Democratic opponents.
Democrats are looking to build on the political momentum that began last year with statewide victories in Virginia, New Jersey and Alabama.
Republicans are hoping for a victory that would confirm the popularity of the Trump tax cuts and the effectiveness of targeting Democratic House leader Nancy Pelosi as a campaign strategy.