Pressure grows on lower tier of 2020 Democrats

Like many in the race, O'Rourke had been unable to break out of a large group of candidates down around 2 percent in many polls, as the former Texas Congressman is not alone in facing a difficult road ahead.

There are others who are being squeezed by outside events in the Democratic race, as Kamala Harris - who for a time was threatening to catch up to the top three candidates - is now shuttering most operations in New Hampshire in order to focus on Iowa.

"The campaign will continue to have a staff presence in New Hampshire," said Harris's spokesman in the Granite State, "but the focus is and will continue to be on Iowa."

A recent poll in New Hampshire showed Harris at just three percent; one reason she has decided to go "all-in on Iowa."

Another candidate making similar choices is Julian Castro, who had already said he would drop out if he could not raise $800,000 in the latter part of October.

While Castro did hit that fundraising goal, his campaign faces much the same difficulties as O'Rourke and Harris - far back in the polls, and unable to break free of the lower tier of candidates.

That led to news this weekend that Castro also won't focus on New Hampshire, and instead look for a boost in on Iowa and the third state on the primary calendar in 2020, Nevada.

The difficulties for candidates like Castro, Harris, O'Rourke and others was driven home on Sunday in the latest Washington Post-ABC News national poll on the Democratic race.

Once you get past Joe Biden, Elizabeth Warren, Bernie Sanders, and then jump to Pete Buttigieg, every other Democratic candidate is at 2 percent or lower.

Also helping to reduce the size of the Democratic field is the qualifying process involving the upcoming debates for Democrats.

Nine candidates are expected in the November debate in Georgia - but so far, only the top four, Biden, Warren, Sanders, and Buttigieg, have qualified for a December debate in Los Angeles.