As speculation swirls about possible running mates, a new poll suggests that the choices made by John McCain and Barack Obama may matter more in this election than usual.

A CBS News survey released yesterday, showing Obama with a 45 percent to 39 percent national lead, reported that 30 percent of voters said the vice presidential pick will have "a great deal of influence" on their vote - double the percentage who said so in the 2000 election. Nearly half of the 13 percent of voters calling themselves undecided said that the choice of running mate will make a difference.

On the veep watch yesterday, Obama campaigned in Indiana with Senator Evan Bayh, who supported Hillary Clinton during the Democratic primaries but is believed to be under consideration by Obama.

Obama called Bayh "one of the finest US senators that we have." Bayh said Obama would bring "a breath of fresh air" to the nation's capital.

On the Republican side, Governor Tim Pawlenty of Minnesota appeared to veer off message a little in an appearance in Arlington, Va., before GOPAC, a Republican political action committee that helps find party candidates.

"Say what you will about Barack Obama," Pawlenty said, "people gravitate when you have something positive to say. People want to follow hopeful, optimistic, civil, decent leaders. They don't want to follow some negative, scornful person."

He added that McCain has been positive as well, and later criticized Obama's experience and resume in comparison with McCain.

THE BOSTON GLOBE AND ASSOCIATED PRESS, August 7, 2008