Karen Tumulty rounds up Republicans whto are supporting or semi-supporting health care reform (Arnold is the latest addition). As Karen notes, none of the Republicans she lists are currently in the house or senate. Ezra Klein has seen this move before:

This is reminiscent of the strategy the Obama campaign employed in the closing weeks of the presidential election. Obama had run as the herald of a new, less polarized type of politics, but he didn't have much support from prominent Republicans. So the campaign began to roll out, or emphasize, retired Republicans: Colin Powell, Jim Leach, and Lincoln Chafee among them. Obama's advisers figured that if the current political situation was too polarized to permit bipartisanship, then they could reach backward, or maybe outward, to find Republicans who weren't subject to its pressures. Then they used the presence of those retired, moderate Republicans to imply that more Republicans would be signing on if not for partisan pressure from the party leadership. Looks like they're readying to run the same play on health care, and they're helped by the fact that it's probably correct on the merits.