TAMPA, Florida — Republican presidential candidate Mitt Romney has a complicated challenge this week at his party’s national nominating convention in Tampa, Florida.

Romney must overcome doubts among some Republicans that he is a true conservative, while at the same time finding a way to appeal to undecided moderate voters for the election in November.

Romney won the Republican nomination through the lengthy process of party primary and caucus elections. But Romney consistently had trouble winning over conservative activists within the party.

Some of Romney’s former rivals for the nomination are rallying around him this week in Tampa in an effort to reassure conservatives and unite the Republican Party.

Former rival Herman Cain remains very popular with conservatives. He told VOA that he’s been working to rally conservative holdouts to the Republican ticket of Romney and Representative Paul Ryan of Wisconsin.

“More and more they are remembering the ultimate mission, and I saw it at our unity rally last night and other places I have spoken,” said Cain. “So, yes they are. They are doing it on the ground and doing the hard work of the foot soldiers.”

The choice of Ryan as Romney’s running mate pleased many conservatives in the party, including another former rival for the Republican nomination, Minnesota Representative Michele Bachmann.

“When they look at Mitt Romney he is solid as a rock. He knows what to do with the economy. This isn’t even a stretch. And the same with Paul Ryan. I know him and I worked with him for six years and I’m very confident about this ticket,” she said.

Romney also has won over conservative foreign policy advocates like the former U.S. ambassador to the United Nations under President George W. Bush, John Bolton. Bolton told VOA he’s confident that Republicans will make a strong case against President Barack Obama’s foreign policy record during the Tampa convention.

“I think what we need is a return to a Reaganite [former President Ronald Reagan] foreign policy of peace through strength, and I think that is what Governor Romney has been talking about, and I think that is the kind of foreign policy he would pursue. And I think we will hear it articulated here at the convention,” said Bolton.

But even as as Romney works to unite the Republican Party this week, he will have to keep in mind millions of undecided voters who are generally not strongly drawn to the ideological leanings of either major party.

Political analyst Norman Ornstein said Romney’s acceptance speech, scheduled for Thursday, will be a critical moment in the campaign.

“Romney wants to be able to have a springboard for his campaign and frame it around the idea that he will govern effectively, while Obama has not,” said Ornstein.

Another analyst, Jeff Greenfield, said Romney must do more than simply offer a critique of the president’s economic record. Greenfield said Romney must offer voters specifics on how he would boost economic growth and jobs.

“But if he doesn’t come up and say ‘Look, I think I have shown you how to make things better,’ then I think voters are likely to shrug and say it’s not a real choice,” said Greenfield.

It’s clear talking to delegates in Tampa that even if some Republicans remain lukewarm about Romney as their presidential nominee, they are united in the goal of trying to deny Obama a second term.