In the wake of Donald Trump's stunning victory over Hillary Clinton for the presidency, Republicans are also celebrating an almost equally unlikely outcome in down-ballot races.  While few gave the Democrats any chance of taking the House, there was almost universal agreement among observers that the GOP's hold on the Senate was in grave danger.

Faced with the task of defending 24 seats compared to just 10 for Democrats, Republican senators rode Donald Trump's coattails to victory.

CNN:

The biggest surprise is that Trump was no drag on the GOP ticket at all -- and might have even helped carry the party.

Trump's margin of victory matched or exceeded those of Todd Young in Indiana and Sen. Richard Burr in North Carolina. Wisconsin Sen. Ron Johnson, who embraced Trump despite expectations the GOP nominee lose his historically Democratic-leaning state, surged late in the race and benefited from Trump's stunning performance there. Incumbents Roy Blunt in Missouri and Pat Toomey won as well, CNN projects.

As of 3 a.m. ET, Republicans held 51 seats to 47 for the Democrats.

The Democrats' lone bright spots were knocking off Illinois Republican Sen. Mark Kirk and holding retiring Senate Minority Leader Harry Reid's seat in Nevada with a victory by Catherine Cortez Masto. There is still a chance in New Hampshire, where GOP Sen. Kelly Ayotte and Democrat Maggie Hassan were neck-and-neck at votes were still being counted.

But there's nothing that will lessen the sting for Democrats.

The Republicans easily held the House, and on a night party officials were confident they'd tip the balance of power in the Senate, Republicans not only remain the majority party -- but appear to head into the 2018 midterms with a map so favorable that a filibuster-proof, 60-seat supermajority is within reach.

The magnitude of the GOP's down-ballot victories was stunning. Its incumbents held seats most Republicans began the 2016 election cycle assuming were lost in some states and overcame weak campaigns in others.

Still to be decided: the Senate race in New Hampshire, where GOP incumbent Kelly Ayotte is holding on to a slim 2,000-vote lead over Governor Maggie Hassan with 95% of precincts reporting as of 8:00 AM eastern.  And there will be a runoff in Louisiana on December 10 between Republican John Kennedy and Democrat Foster Campbell, with Kennedy besting Campbell by 8 points. 

Predictions prior to election day had the Democrats gaining 12-15 House seats.  At the moment, the Dems look as though they will gain 6-8 seats.  It seems likely that Trump aided several House races as well.

President Trump will have a GOP House and Senate to deal with – the first time Republicans have possessed the House, Senate, and White House since 2007.  But the party is still bitterly divided, and it will take all of Trump's negotiating skills to get his agenda passed.