Key Senate Republicans have voiced optimism about Donald Trump’s presidential prospects in November as he added two more primaries to his column.

Mr Trump took West Virginia and Nebraska, as senior party figures gave the clearest signal yet to the rank and file to unite behind the bombastic billionaire and turn their energy against Democrat Hillary Clinton.

“We have a nominee, it looks like he may well be very competitive, and we want to win the White House,” Senate majority leader Mitch McConnell said.

He added: “We know that Hillary Clinton will be four more years of Barack Obama. I think that’s going to in the end be enough to unify Republicans across the country.”

But doubt over Mr Trump remained palpable as policy-makers returned from a week-long recess that saw him effectively clinch the presidential nomination.

Tim Scott of South Carolina offered his support, but like others managed to sound grudging and backhanded in the process: “I’m supporting the Republican candidate, and it happens to be Donald Trump.”

Johnny Isakson of Georgia said: “The only thing I can do is get re-elected so we have a Republican majority in the Senate. I will support the Republican ticket and I’m endorsing me for my Senate seat.”

The comments reflected ongoing divisions in a party still reeling over Mr Trump’s success in locking up the nomination and pushing his two remaining rivals from the race last week. Mr McConnell and others have decided that the best approach is to get behind Mr Trump, but especially in light of House Speaker Paul Ryan’s surprise decision to withhold his support, unity is elusive.

That could start to change on Thursday, when Mr Ryan, Mr McConnell and other congressional Republicans meet Mr Trump.

Mr Ryan defended his stance again on Tuesday, insisting that he was just being honest in saying Mr Trump had more work to do to show he could unify the party after alienating numerous voters including women, Hispanics and many conservatives.

Meanwhile, Bernie Sanders added another state to his tally against Ms Clinton with a win in West Virginia, but it will do little to slow his rival’s steady march towards the Democratic nomination.

Ms Clinton entered the night fewer than 200 delegates shy of the 2,383 she needs to secure the nomination. To win it, she needs just 17% of the delegates at stake in the remaining contests.

That means she could lose all the states left to vote by a landslide and still emerge as the nominee, as long as all of her supporters among the party insiders known as superdelegates continue to back her.

Ms Clinton has already largely shifted her focus to the general election and Mr Trump.

Ms Clinton won the Democratic primary in Nebraska, but the victory does not take her any closer to clinching her party’s nomination.

That is because Nebraska allocated all 25 of its delegates to this summer’s Democratic National Convention in a caucus held on March 5 that was won by Mr Sanders. He took home 15 delegates from that caucus, while Ms Clinton won 10.