Former Rep. Pat Toomey (R) has reclaimed a narrow lead in Pennsylvania's exceedingly close Senate race, according to a poll released Monday.

The Morning Call/Muhlenberg College daily tracking poll of the race found Toomey leading Democratic Rep. Joe Sestak 47-42 percent, with 11 percent undecided.

The poll surveyed 437 likely voters in Pennsylvania and has a margin of error of 5 percentage points.

Sestak made up ground on Toomey in recent weeks in the closely watched contest, but Monday's poll suggests Toomey could be heading off that momentum. Three polls last week showed the Democrat and the Republican running in a dead heat after Toomey had led the race for weeks.

That caused White House senior adviser David Axelrod to say last week the "momentum has shifted" back to the Democrats side, which the Toomey campaign refuted. 

The White House has made the Pennsylvania Senate race a top priority for maintaining the Democrats' majority in the upper chamber in the face of a potential Republican wave.

President Obama two weeks ago headlined a large rally in Philadelphia to mobilize the Democratic base that polls show is trailing Republicans in voter enthusiasm.