(CNN) - A new poll released Friday indicates Republican presidential candidate Mitt Romney has expanded his lead over Rick Santorum to its widest margin in weeks.
Romney has the backing of 40% of registered Republicans nationwide, while Santorum comes in with 26%, according to Gallup's daily tracking poll.
- Follow the Ticker on Twitter: @PoliticalTicker
The 40% threshold also marks the highest point ever for Romney (or any other candidate) since the daily survey began measuring support in early November.
The poll shows a six-point increase for Romney since Tuesday, the same day he won the Illinois primary. Meanwhile, Santorum dropped four points in the same time period.
Results from Friday's poll, which was conducted Sunday through Thursday, includes responses that came partially after Romney's victory in the Land of Lincoln earlier in the week.
The poll shows little movement for the other two Republican presidential candidates in the last few days. Former House Speaker Newt Gingrich remains relatively steady at 14%, while Texas Rep. Ron Paul has slight decline to 8%.
In a rare day for the primary season, all four GOP candidates are campaigning in the same state Friday as they compete for the 20 delegates at stake in Louisiana's primary on Saturday.
For the ongoing poll, Gallup surveys more than 1,000 registered Republican voters on a daily basis, and the poll drops the oldest of five days each day and adds results from the most recent day of polling.
In the latest survey, Gallup questioned 1,157 Republicans and Republican-leaning independents by telephone March 18-22, with a sampling error of plus or minus three percentage points.