Minnesota Gov. Tim Pawlenty has collected more than $500,000 in contributions for Arizona Sen. John McCain, the presumptive Republican nominee for president.

Pawlenty is national co-chairman for McCain's campaign. Among governors mentioned as potential running mates, he is the only one in the ranks of top McCain "bundlers" -- that is, those listed as having raised more than half a million dollars.

The list, updated Tuesday on McCain's website, was welcomed by the Center for Responsive Politics and other campaign watchdog groups who have pressed both McCain and Democrat Barack Obama to make their online rosters of big donors more transparent.

The $500,000-plus category is a new one for the McCain camp. It used to max out at $100,000-plus. Obama's top bundler tier maxes out at $200,000, according to the Center for Responsive Politics, which is holding out for a $1 million-plus disclosure category.