Polling data that weeks ago heavily favored Democrats to win control of the Senate and gave them a fighting chance to capture the House of Representatives now suggest the Senate is a toss-up and Republicans are all but certain to retain their House majority in Tuesday's vote.
The erosion in Democratic legislative prospects coincides with the FBI's review of a new batch of emails linked to Hillary Clinton, announced October 28, and with the unveiling of jaw-dropping increases in premiums for health care plans under the Affordable Care Act, also known as Obamacare.
“Tightening of the presidential race — before and after [FBI Director James] Comey's first letter to Congress — likely spilled over to tighten up these competitive Senate races," said political analyst Sarah Binder of the Washington-based Brookings Institution.
Republicans gain ground
Final pre-election polls give an edge to Democratic candidates vying to unseat incumbent Republican senators in Illinois, Wisconsin, and Pennsylvania and for Democrats to retain the seat of retiring Minority Leader Harry Reid in Nevada.
But Democrats would need a net gain of four seats for a Senate majority if Hillary Clinton is elected president, five if Donald Trump is victorious. In the remaining competitive races, all have seen an uptick in polling numbers for Republican incumbents, with only New Hampshire and North Carolina seen as true toss-ups.
In North Carolina, Republican Senator Richard Burr has sought to capitalize on double-digit Obamacare premium hikes in his state.
"It's clear that #Obamacare is not working," Burr recently wrote on Twitter. "I will work to replace this disaster with patient-centered reforms."
Email probe a factor
A Quinnipiac poll released on the eve of the election has Burr tied at 47 percent with Democratic challenger Deborah Ross.
Like many Democrats, Ross has tied her opponent to the Republican presidential nominee, running television ads featuring video in which Burr said he was "fully supportive of Donald Trump."
But that strategy may have lost clout as Clinton's national lead eroded amid the renewed email probe and Trump appeared to gain momentum last week. It's no surprise that Republican lawmakers have fared better in polls at a time when the top of the ticket appeared to get a bounce, according to Binder.
"The races seem tighter as Republicans became more willing to answer pollsters when Trump's prospects rose," she said.
Sunday, Comey informed lawmakers that, once again, no charges would be brought against Clinton for her handling of electronic communication as secretary of state. The announcement's effect on polling numbers is impossible to know, since pre-election surveys of voters at the national and state level were completed before Comey's letter was sent.
If continued Republican control of the Senate is tenuous, the party's grip on the House of Representatives seems assured. Democrats would need to gain 30 seats in the chamber, where only about 40 are considered competitive.
"Democrats are likely to pick up maybe a dozen seats," Binder said.
Ryan's future unsure
The impact of a reduced Republican majority could be significant if the caucus loses its more moderate members, making the ultra-conservative Tea Party faction, or Freedom Caucus, more potent.
"Ryan's ability to be re-elected speaker will depend significantly on how large the [Republican] majority is and how many of his loyalists lose Tuesday night," said political analyst John Hudak, also at Brookings.
Already, some Tea Party House members have refused to say whether they would support Ryan in the new Congress, leading to speculation that Ryan, who assumed the post reluctantly after the resignation of John Boehner last year, could step down.
"Ryan's failure to be re-elected [speaker] could pose even more significant challenges for the party at the outset of the new Congress," Hudak said.