Vice President Joe Biden considers challenging Hillary Clinton in Democratic primary

NEW YORK (WABC) -- In the race for president, the contest could be getting more interesting on the Democratic side.

Vice President Joe Biden is making phone calls and having meetings as he considers challenging Hillary Clinton for the Democratic primary.

So who would get President Obama's support if Biden joins the race?

This sets up a dilemma for the president.

The White House Monday indicated Obama may make an endorsement in the Democratic primary, and so he'd be forced to choose between two of his closest advisors.

Over the weekend, it was a secret and hastily arranged meeting between the vice president and liberal icon Elizabeth Warren.

With the president back from vacation, Biden Monday lunched with Obama. Reporters asked about it, and maybe it was unintentional, but the White House was nice about Clinton and even nicer about Biden.

"The president has indicated his view, that the decision he made I guess seven years ago, to add Joe Biden to the ticket as his running mate was the smartest decision he had ever made in politics," said John Earnest, the White House Press Secretary.

Biden requested the one-on-one sit down with Warren as he edges closer to a run.

Warren has refused to endorse anyone in the race.

"I want to see all of the Presidential candidates lay out where they stand on key issues," Sen. Elizabeth Warren, (D) Massachusetts.

The super PAC Draft Biden is also ramping up it's efforts in case the vice president decides to make a third run for the White House.

"I think Joe Biden can win this presidential race," Josh Alcorn told ABC News White House Correspondent Jonathan Karl. "There's a real enthusiasm for a kind of candidate like him, somebody who can look somebody in the eye, connect with them on a very real level, tell them what he thinks the issues facing the country are and then back his words up with actions."

Alcorn, a top strategist for former Delaware Attorney General Beau Biden, joined the campaign as a senior adviser.

Over the weekend, Clinton supporter Bill Richardson doubted Biden will run. Biden just lost his son, beau, a few weeks ago, to brain cancer.

"I don't think he gets in, I think the personal situation he's going through and the fact Hillary Clinton is way ahead, I don't think he gets in," said Bill Richardson, (D) Former Governor of New Mexico.

But the email scandal is eroding support for Hillary. One recent poll found only 37% see Clinton as honest and trustworthy; compare that to Biden at 58%.

On the Republican side, Donald Trump weighed in on the Democratic primary.

"Would he be a tougher opponent than Hillary? I don't think so. I think they're the same," Trump said.

And Trump just keeps gaining momentum, no matter what he says.

Monday on the stock market mess, Trump trashed China.

"China is taking our jobs, they're taking our money, be careful. They'll bring us down. You have to know what you're doing. We have nobody that has a clue," Trump said.

Joe Biden is set to make his decision on running sometime in late September or early in October.

That timetable is affected by the first Democratic debate; it's scheduled for October 13th.