Washington (CNN) A new poll shows Donald Trump still holds a strong lead over his challengers in the 2016 Republican primary field.

The Pew Research Center poll, released Friday, shows Trump with 25% support from likely Republican voters nationwide. Retired neurosurgeon Ben Carson grabbed 16% support, Florida Sen. Marco Rubio and former Hewlett-Packard CEO Carly Fiorina got 8% each and Texas Sen. Ted Cruz garnered 6% support.

Meanwhile, Jeb Bush -- at one time the front-runner in national polls himself -- garnered 4% support.

The poll, conducted between Sept. 22 and Sept. 27, asked possible voters an open-ended question of who they would support for the Republican nomination. Unlike some other surveys, pollsters did not provide a list of names.

There was strong name recognition for Trump, but 25% of respondents said they did not know who they would vote for at this point -- just four months away from the first primary.

Read More