Bernie Sanders to endorse Hillary Clinton at New Hampshire rally

Democrat Bernie Sanders will team up with Hillary Clinton on the campaign trail for the first time on Tuesday, joining her in New Hampshire, where he is expected to endorse her White House campaign in a belated show of party unity.

Five weeks after Clinton clinched the Democratic presidential nomination, the U.S. senator from Vermont is scheduled to join her at a rally designed to put their bitter primary campaign behind them and emphasize a shared commitment to beating Donald Trump, the presumptive Republican nominee, in the Nov. 8 election.

The appearance in Portsmouth, New Hampshire, concludes weeks of negotiations between the two camps and comes after Clinton last week adopted elements of Sanders' plans for free in-state college tuition and expanded affordable healthcare coverage.

The event is also less than two weeks before the opening of the Democratic National Convention in Philadelphia, where Clinton is expected to become the party' official nominee.

Sanders also successfully pushed to include an array of liberal policy positions in the Democratic platform, which a committee approved on Saturday. His campaign described the platform in a statement as "the most progressive in party history."

Sanders did not win all of his policy fights, most notably failing to win support for blocking a vote in Congress on the Trans-Pacific Partnership trade deal. But he told reporters on Saturday that the two campaigns were "coming closer and closer together."

Clinton hopes the joint appearance will help her win over Sanders supporters. In recent Reuters/Ipsos polling, only about 40 percent of them said they would back her.

But top Democrats including President Barack Obama and Senator Elizabeth Warren of Massachusetts, a favorite of the party's liberal wing, have already announced their support for Clinton, leaving Sanders at risk of being left behind in the Democratic battle against Trump.

"I think all signs point to the fact that we're going to have a very united party going into Philadelphia," Clinton campaign spokesman Brian Fallon said on CNN, "and when you compare it to the Republicans, we're going to be miles ahead of them."

Trump has struggled to unify the party after alienating many establishment figures with his stances on immigration, Muslims and women. A number of prominent Republicans are skipping the party's national convention in Cleveland next week.

In another sign of the Democrats' growing unity, two prominent liberal groups that had backed Sanders, the Communications Workers of America labor union and the Congressional Progressive Caucus PAC, announced their support for Clinton on Monday.

The congressional group is led by two of Sanders' biggest backers in Congress - Raul Grijalva of Arizona, who already had endorsed Clinton, and Keith Ellison of Minnesota.

"With the Democratic Party on track to ratify the most progressive platform in recent history, and Clinton continuing to campaign on progressive ideas, Sanders supporters can feel good that they helped to transform the future of the Democratic Party and America," said Kait Sweeney, a spokeswoman for the liberal Progressive Change Campaign Committee and a former Sanders campaign staffer.

New Hampshire is where Sanders first served notice of the strength of his campaign by beating Clinton handily in the primary.

Also, Clinton and Obama held their first joint rally there in 2008 after his victory in that brutal primary race. To make sure everyone got the point, it took place in the town of Unity.

(Editing by Leslie Adler and Lisa Von Ahn)