President Trump's senior campaign advisor Steve Cortes on Monday said that national polls don't decide elections and look better for Democratic nominee Joe Biden because of an oversampling of Democratic voters.

Speaking on Fox News's "Bill Hemmer Reports," Cortes said, "I think polls matter. We pay some attention to them. It’s very critical to look at the inputs into these polls because the inputs often determine the final output numbers. And many of these polls — I haven’t looked at this one yet specifically, but many of these polls have massive oversampling of Democrats."

In the segment, Hemmer referred to a recent Washington Post-ABC News poll that showed Biden with a 12-point lead over Trump. The survey had a sample size of 1,014 adults with a margin of error of 3.5 percentage points. Among those who participated in the poll, 30 percent identified as Democrat, 27 percent identified as Republican and 35 percent identified as independent.

Cortes pointed to polling data in battleground states and said that it shows the election is a toss-up. A recent poll released by Baldwin Wallace University showed the president trailing Biden in Michigan, Wisconsin and Pennsylvania, three battleground states Trump won in 2016. The RealClearPolitics average of polls shows Biden with a nearly 5-point lead in the sampling of battleground states.

During the interview, Hemmer asked Cortes about Trump's health following his recent coronavirus diagnosis. The campaign adviser said the president was in excellent health and was "100 percent." When asked if it was true that Trump wanted to host a rally every night day until Election Day, Cortes remained coy, saying, "I can’t speak beyond this week’s schedule, but this week, yes, every day."