Democrats hold leads in two marquee Senate races in Virginia and New Mexico, according to new polls released by the Democratic-affiliated Public Policy Polling firm.

Former Virginia Gov. Tim Kaine (D) holds a 47 percent to 42 percent edge over former Sen. George Allen (R-Va.), while Rep. Martin Heinrich (D-N.M.) leads former Rep. Heather Wilson (R-N.M.) by 47 percent to 40 percent.

The two seats are currently held by Democrats and are top Republican targets. It becomes much harder for the GOP to regain control of the Senate if they lose both these races.

Democrats currently hold 53 Senate seats, meaning if President Obama wins reelection the GOP needs to net four seats to take control of the chamber. Democrats are defending 23 seats this election, while Republicans are defending 10 seats.

Kaine's lead comes from a 43 percent to 39 percent edge with Independents. He has held a very narrow lead over Allen in most public polls, and this is the largest lead he has held in any public poll since the campaign began. Kaine and Allen debated for the first time last week, a contest most observers said Kaine won.

Heinrich and Wilson are both in contested primaries, although the poll shows they both hold comfortable leads at this point over their opponents. Heinrich leads New Mexico State Auditor Hector Balderas (D) by 47 percent to 30 percent, while Wilson leads New Mexico Lt. Gov. John Sanchez by 55 percent to 20 percent.

Heinrich's lead over Wilson in the Democratic-leaning state has remained almost unchanged since the last time PPP polled the state.

The two seats are held by retiring Democratic Sens. Jim Webb (Va.) and Jeff Bingaman (N.M.), respectively.

The New Mexico poll of 500 voters has a margin of error of 4.4 percentage points, while the Virginia poll was of 600 voters with a margin of error of 4.0 percentage points.