Republicans fretting that Donald Trump will lose them control of both houses of Congress

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Congressional Republicans are grumbling that a Trump at the top of the ticket could kick GOP majorities off Capitol Hill. 

'There are people that couldn't win if he was our nominee,' warned Rep. Steve Stivers, an Ohio Republican and the deputy chairman of the National Republican Congressional Committee, the group responsible for getting Republicans elected to the House. 

Stivers made his complaints to Politico, as reporters interviewed a number of Republicans who aired their concerns, capturing the jittery atmosphere the billionaire's campaign has created on the capitol campus.

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If current frontrunner Donald Trump tops the Republican ticket, Congressional Republicans fear he'll cost the party control of Congress, with their Senate majority only four seats deep 

Endangered Species? Senate Majority Leader Mitch McConnell (left) and House Speaker Paul Ryan (right) are lording over GOP majorities on Capitol Hill now - but Republicans are fretting that The Donald could damage the brand and send enough Republicans home to give Democrats control of the House and Senate yet again 

Stivers was the most blunt, saying that Donald Trump, especially in light of his most recent policy prescription – to ban non-American Muslims from entering the United States – would be a down-ballot loser. 

'It would be devastating to our attempts to grow our majority and would cost us seats,' Stivers told Politico. 

Oregon Rep. Greg Walden, the chairman of the NRCC, was also critical of Trump's policy on Muslims and outlined the electoral cost. 

''It puts, certainly, competitive seats in jeopardy,' he said. 'We'll have a much more difficult time.' 

'People have to be very careful about what they say at all times,' he continued. 'And this, as Speaker Ryan said today, this is not what we're about as a party; this is not what we're about as a country.' 

New House Speaker Paul Ryan condemned Trump's remarks at a press conference yesterday. 

'Some of our best and biggest allies in this struggle and fight against radical Islamic terror are Muslims,' Ryan said. 'The vast, vast, vast, vast majority of whom are peaceful who believe in pluralism, freedom, democracy, individual rights.' 

Republicans have a better hold of the House since it flipped in 2010 thanks to a Tea Party takeover, which handed former Speaker John Boehner the gavel and ripped it away from Democrat Nancy Pelosi, now the House Minority Leader. 

Not Nancy! House Minority Leader Nancy Pelosi (left) could get her old job back if enough seats turn blue in 2016, a prospect that worries Republicans. While liberal Sen. Chuck Schumer is poised to take Harry Reid's job leading the Senate Democrats, which could again become the majority party in the Senate 

In the Senate, however, Republicans are finding themselves in the position Democrats were in last year: defending a lot of seats, 24 to be exact, and trying to hold onto a four-seat majority.  

'In the Senate, where the majority is even more tenuous, lawmakers are practically running from the question,' Politico reported.  

With Senate Minority Leader Harry Reid retiring, New York Sen. Chuck Schumer is poised to lead the Senate Democrats. 

He's been viewed as a liberal boogeyman of sorts, with both Marco Rubio and Ted Cruz, also running for president, using each other's proximity to Schumer on particular issues as political attacks against each other. 

In the House, Nancy Pelosi could once again take the gavel, another prospect that could bring Republican party faithful to the polls, but probably not negate voters coming out to vote against Trump and for the Democratic nominee. 

'Nothing will impact our majority more than who we nominate for president,' Rep. Tom Cole, R-Okla., told Politico. Cole formerly chaired the NRCC in 2005 and 2006. 

'I think it's very hard to put a great deal of distance between yourself and your presidential nominee in either a winning or losing year,' Cole continued. 

'At the end of the day, you have to recognize the presidential nominee of both parties has the biggest megaphone out there other than the president himself,' he added.