ABC News’ Michael Falcone reports:

The presidential foot traffic to Donald Trump’s doorstep is showing no signs of letting up.

On Thursday, the real estate mogul welcomed Michele Bachmann for a repeat visit to his Trump Tower office in New York City, and in an interview with Fox News’ Greta Van Susteren Thursday night, Trump said that Bachmann is “really working hard” on her presidential bid.

“In fact,” Trump said, ” I was saying, take it easy, relax.”

Trump said he was “impressed with her,” but declined to tell Van Susteren who he planned to endorse in the Republican primary, noting that he would do so at “the appropriate time.”

On Fox, Trump acknowledged that Texas Gov. Rick Perry is “having a hard time with the debates,” said that Mitt Romney “doesn’t seem to be getting much of a bounce” from his solid debate performances and said that Herman Cain has done an “amazing” job capitalizing on his new-found momentum.

Trump has entertained most of the major presidential candidates during the course of the primary season. He recently sat down with Cain and Romney and, before that, had dinner with Perry and Sarah Palin, who opted against a presidential run. In New Hampshire on Monday Bachmann said she is ”re-booting” her campaign, and courting Trump appears to be part of her strategy.

“The breakfast meeting with Michele Bachmann this morning is yet another example of how important Donald Trump’s endorsement is to the potential GOP candidates,” said Michael Cohen, Trump’s top political adviser. “A recent poll by The Polling Company showed that 77 percent of all voters want to see a president who is not a politician and possesses both national and international business experience. Anyone reading this poll would clearly think that they were talking about Donald Trump. It is this sentiment from the public that keeps the candidates coming back for more face time.”

And, as Trump told Van Susteren, it’s not only 2012 candidates who are in touch.

Trump said he recently spoke on the phone with Sen. Lindsey Graham, R-S.C. The politician and the reality television star talked about China, Trump said.

“I love what he’s doing with respect to China,” said Trump, who praised Graham for pushing a bill that aims to take a hard line on currency manipulation. “He should be given more support.”