Beto O'Rourke Beto O'RourkeJimmy Carter says his son smoked pot with Willie Nelson on White House roof O'Rourke endorses Kennedy for Senate: 'A champion for the values we're most proud of' 2020 Democrats do convention Zoom call MORE on Sunday he's not disappointed by the start of his presidential campaign.

"I knew this was going to be tough, it's perhaps one of the hardest things that one can do," the former Texas lawmakers said in an appearance on NBC's "Meet the Press."

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"We're not gonna be able to accomplish this in just one media cycle or in a couple of months. It's a long, hard-fought campaign," he added.

O'Rourke entered the Democratic primary to great fanfare and late last year was even seen by some as a favorite to win the primary.

But he's struggled to win momentum and has seen his polling numbers fall. He's well behind former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE and Sen. Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE (I-Vt.).

O'Rourke has also been eclipsed by South Bend, Ind. Mayor Pete Buttigieg Pete ButtigiegThe Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice Hillicon Valley: FBI, DHS warn that foreign hackers will likely spread disinformation around election results | Social media platforms put muscle into National Voter Registration Day | Trump to meet with Republican state officials on tech liability shield MORE.

O'Rourke gained mass attention during his 2018 campaign against Sen. Ted Cruz Rafael (Ted) Edward CruzCruz blocks amended resolution honoring Ginsburg over language about her dying wish Trump argues full Supreme Court needed to settle potential election disputes Press: Notorious RBG vs Notorious GOP MORE (R-Texas).