ABC News' Bret Hovell Reports: Sen. Joseph Lieberman called on Michigan's Independents and Democrats on Tuesday to come out and vote for Sen. John McCain in the Republican primary, saying he is convinced that McCain will "become our next great American president."
"I urge them to come out today and stand for a man who is a great American patriot," Lieberman said at a joint town hall meeting with McCain in Ann Arbor, Mich.
"There's no competitive Democratic primary," Lieberman added. "I know there's some other moderate and conservative Democrats like myself."
Lieberman, an Independent Democratic senator from Connecticut, crossed party lines to endorsed McCain, R-Ariz., for president last month. He has appeared on the trail with McCain, and occasionally spoken in his place.
Michigan's primary - underway Tuesday - is open, meaning it allows voters to pick which ballot – Republican or Democrat – they wish to use. The frontrunners for the Democratic primary are not competing here in the Great Lakes state.
Lieberman and McCain share an ideological kinship on the issue of the Iraq war, and have traveled to Iraq together on congressional delegation trips.
McCain's rival for the Republican nomination, former Governor Mitt Romney, R-Mass., suggested Tuesday that if McCain wins in Michigan, it will be because of the crossover votes from non-Republicans.
"Many people predicted that in New Hampshire we wouldn't get the majority of the Republican vote. We did," McCain responded to reporters. If [Independents and Democrats] all turn out for us, then I think that's a signal that we can do well in the general election."
McCain was also asked if Lieberman might be a potential running mate for him if he were to win the nomination.
"I think it would be very presumptuous of me having won one primary to be discussing running mates," McCain said. "Now I'll admit to a massive ego, but not quite that massive."