As the US presidential race enters its frantic final 72 hours, a battle for Congress is also coming down to the wire, with the fate of the Senate teetering on a knife's edge.

Who runs the two chambers -- and the legislation introduced there -- is crucial, as bills can easily get stuck, particularly if the leadership does not belong to the same party as the president.

Both the Senate and the House of Representatives are currently under Republican control.

Last week, it was looking likely that Democrats would ride Hillary Clinton's coattails on November 8 and reclaim the Senate.

But then FBI Director James Comey entered the fray, and all bets are off.

Comey told congressional leaders on October 28 that the bureau, having discovered a fresh batch of emails that might be pertinent to an earlier probe of Clinton's private email server, was taking another look into the case.

Suddenly, national polls tightened, and congressional Republicans in tough re-election battles gleefully pounced on the news to remind voters of the importance of securing a check against a possible Clinton presidency.

Republicans enjoy a strong 59-seat majority in the 435-member House of Representatives, and most analysts say it would take a so-called 'wave election' -- when one party makes major gains in Congress -- for Democrats to flip the 30 seats needed to retake control.

"House generic polling averages don't indicate a wave is coming in the lower chamber," wrote a team of analysts from the University of Virginia's Center for Politics.

Attention falls therefore on the 100-member Senate, where Democrats would need to gain four seats for a majority in the event Clinton wins the White House, as ties in the Senate are broken by the vice president.

"I think having a Democratic Senate is absolutely critical," Clinton said Saturday on American Urban Radio Networks, explaining why she is pushing hard for candidates in states like Florida, North Carolina and Pennsylvania.

The million-dollar question is: how much could an allegiance to Donald Trump impact the Republican Party's chances at the ballot box?

Trump a 'double-edged sword'

"In isolated cases, it may allow some Republicans in close races to win re-election by distancing from Trump," George Washington University professor of applied politics Gary Nordlinger told AFP.

"But it's a real double-edged sword. Trump is wildly popular among his base, so you risk alienating that base when you try to distance yourself."

Republicans were struggling last week, but the FBI bombshell has lifted spirits.

On Saturday, the FiveThirtyEight website, featuring respected election forecaster Nate Silver, dropped its chances of Democrats winning the Senate from 72.8 percent to 53 percent.

Cook Political Report had projected Democrats would pick up five to seven seats. But it shifted its rating for the Wisconsin race from leaning Democrat to a toss-up.

Of the Senate's 34 seats contested in 2016, 24 are held by Republicans, making it a tough year for the GOP. Of the nine closest Senate races, only one, in Nevada, is held by a Democrat.

Illinois is likely to flip to the Democrats. Another vulnerable Republican is in New Hampshire -- although Senator Kelly Ayotte surged into the lead against the state's Democratic Governor Maggie Hassan just before the FBI news landed.

North Carolina and Pennsylvania could tip to Democratic blue, with tougher but still viable battles in Florida and Indiana.

Even red-leaning Missouri is in play. Republican Senator Roy Blunt risks losing to Jason Kander, a charismatic Democratic military veteran whose campaign video of himself assembling an AR-15 rifle while blindfolded has gone viral.

With Republicans scrambling to preserve the Senate, a conservative group is pouring $25 million into a half-dozen races.

"We know that it will be a tough challenge to keep the Senate in this environment, but if Democrats want the majority, they are going to have a hell of a fight on their hands," Ian Prior of the Senate Leadership Fund said last week.

Clinton welcomes that fight, and has sought to drape Trump around Republicans' necks like an albatross.


jpegMpeg4-1280x720The House is the Republican firewall.

Speaker Paul Ryan has had a tempestuous relationship with Trump, and after the nominee's lewd comments about women emerged last month, Ryan said he could no longer defend or campaign with the candidate.

Instead he is focusing on maintaining his House majority.

Still, most of the vulnerable House seats are held by Republicans, and Democrats are confident they can cut deeply into the GOP's majority, perhaps regaining as many as 10 or 15 seats.

A confident Clinton camp is making forays into House races, seeking to pick off seats where Republican incumbents are in jeopardy.

One pro-Clinton group released an ad in Iowa tying freshman congressman Rod Blum to Trump.

It shows footage of Blum at a campaign rally saying, "Send me back to Congress, and you send Donald Trump to the White House."