Three weeks into a partial shutdown of the federal government, President Donald Trump and opposition Democrats remain sharply divided over the president's demand for a border wall with Mexico.Trump believes that delivering on his campaign promise of a border wall is crucial to his re-election hopes next year. Opposition Democrats feel just as strongly that they need to stop him to show what their party stands for.In some ways, the shutdown drama may serve as a kind of dress rehearsal for the next presidential campaign in 2020.Prime-time pitchTrump made his latest forceful push to get public opinion on his side with his nationally televised address Tuesday calling attention to what he said is a humanitarian and security crisis along the southern border. "Democrats in Congress have refused to acknowledge the crisis and they have refused to provide our brave border agents with the tools they desperately need to protect our families and our nation," Trump said in his speech.Democrats oppose the wall and believe Trump is holding the country hostage simply to deliver on a core campaign promise."Most presidents have used Oval Office addresses for noble purposes," said Senate Democratic leader Chuck Schumer. "This president just used the backdrop of the Oval Office to manufacture a crisis, stoke fear and divert attention from the turmoil in his administration."Schumer gave the official Democratic response to the president's speech alongside House Speaker Nancy Pelosi. Among those watching the president was Texas supporter Jeneria Lewis, who told the Associated Press that she approved of Trump's demand for a border wall."It was a plea," she said. "I saw a logical plea and I support it."But those put out of work by the partial government shutdown are frustrated, including Mike Gayzagian in Massachusetts who works for the Transportation Security Administration."By essentially holding hostage our paychecks while they fight amongst themselves over political issues is unfair. It is unfair to everybody," he told AP.Keeping a promiseTrump fueled his rise to the presidency with a campaign promise to build a border wall. He is now under pressure from conservatives to follow through, according to University of Virginia analyst Larry Sabato."Essentially, they said, 'If you don't push harder for your wall and you don't get billions of dollars to build it then your base, and we represent that base, won't be there for you in 2020,'" Sabato told VOA via Skype.Immigration is also a touchstone for opposition Democrats who oppose the border wall and the president's overall hardline approach to the issue. "It is about the treatment of immigrants at the borders. It is about the separation of families," Sabato said. "This is a human rights issue. It is not just about border security."Base strategyConfronted with historically weak poll ratings two years into his term, Trump seems primarily focused on pleasing his base. But some experts suggest that is a risky strategy."I haven't seen President Trump move from a campaigning mode to a governing mode, and the base seems to have a magical relationship with him in his mind, and somehow he has not tried to move well beyond that," said historian Doris Kearns Goodwin in a recent VOA interview. "He just simply wants to make sure he does not lose them."Trump may have had some recent poll numbers in mind when he delivered his nationwide appeal Tuesday. A new Politico/Morning Consult poll found that 47 percent of those surveyed mostly blamed the president for the shutdown, compared to 33 percent who put more blame on Democrats. In the same survey, voters narrowly opposed a border wall with Mexico, 47 against to 44 percent in favor. In terms of political strategy, Trump seems to believe that his path to re-election lies along a border wall that has yet to become a reality.Democrats, including many of those preparing to run for president next year, seem equally determined to deny him a political victory just as the 2020 campaign is about to begin.