Roll Call is reporting:

If security sweeps are the giveaway, former Massachusetts Gov. Mitt Romney may be on the brink of being selected as Sen. John McCain's (R-Ariz.) vice presidential running mate.

According to sources with strong Michigan ties, the Secret Service has conducted a security sweep of the home of Romney's sister. Romney was raised in Michigan, where his father served as governor.

However, one campaign operative familiar with the working of a presidential-level campaign cautioned that a sweep of such a location could have been conducted in advance of Romney appearing as a surrogate -- not the vice presidential nominee -- at an upcoming McCain campaign stop in Michigan.

Which means this isn't quite the same thing as when we learned Biden was getting Secret Service protection. Take it for what it's worth now. There are also reports that Tim Pawlenty has cancelled many of his afternoon and tomorrow engagements.

Get the latest VP news in the VP Watch blog.