4) As Thursday's petition submission deadline approaches, it appears that Tim Kaine will be the only Democrat on the Virginia Senate primary ballot while George Allen could face four opponents. 3) How is the congressional ethics probe of Rep. Shelley Berkley, D-Nev., going to play in the Senate race? Jon Ralston writes, "if this is, as I believe, a margin of error race, this issue could be the margin of victory for Heller. If, that is, the panel decides to move forward this summer with a full-blown probe, ensuring the shadow will reach until November." 2) Milwaukee Mayor Tom Barrett is using the RGA ad that attacks both him and former Dane County Executive Kathleen Falk to raise money. Falk, meanwhile said Barrett has had his chance to defeat Gov. Scott Walker, and should back her candidacy. Barrett would be a formidable contender. Falk knows this, so do the Republicans. That's why both sides are pouncing. 1) Rick Santorum won the Louisiana primary with nearly 50 percent of the vote, but the April contests in the northeast should be friendlier to Mitt Romney. Meanwhile, Santorum is facing more pressure to drop out and Romney is picking up more high profile support: House Majority Whip Kevin McCarthy endorsed him on Monday and Sen. Mike Lee, R-Utah, endorsed him on Sunday.