Democratic presidential candidate Beto O'Rourke said on Thursday he was resuming his campaign with a new sense of focus after a mass shooting in his Texas hometown, while rival John Hickenlooper ended his bid to take on President Donald Trump.

Both men have struggled with low opinion poll numbers in the historically large field of candidates running for president in 2020, and both have faced mounting calls to run instead for competitive U.S. Senate seats in their respective states.

O'Rourke, a former congressman from El Paso, rejected the idea. After a gunman targeting Mexicans killed 22 people at a local Walmart store on Aug. 3, O'Rourke said he would now use his platform as a presidential candidate to highlight the plight of immigrants and confront what he characterized as Trump's racially charged and divisive rhetoric.