Given the following context:

The painting depicts a harpist, a woman who at first glance appears to be sitting atop a great mountain. Until you take a closer look and see that the woman is bruised and bloodied, dressed in tattered rags, the harp reduced to a single frayed string. Your eye is then drawn down to the scene below, down to the valley below, where everywhere are the ravages of famine, the drumbeat of war, a world groaning under strife and deprivation. It is this world, a world where cruise ships throw away more food in a day than most residents of Port-au-Prince see in a year, where white folks' greed runs a world in need, apartheid in one hemisphere, apathy in another hemisphere ... That's the world! On which hope sits! [...] And yet consider once again the painting before us. Hope! Like Hannah, that harpist is looking upwards, a few faint tones floating upwards towards the heavens. She dares to hope ... she has the audacity ... to make music ... and praise God ... on the one string ... she has left!
Wright's sermon left a great impression on Obama, who recounted Wright's sermon in detail in his memoir Dreams from My Father. Soon after Dreams From My Father was published he went into politics, entering the Illinois Senate. In 2004 he was chosen to deliver the keynote address at the 2004 Democratic National Convention. In Obama's 2006 memoir The Audacity of Hope, he recollects that on being chosen to deliver this speech, he pondered the topics on which he had previously campaigned, and on major issues then affecting the nation, before thinking about the variety of people he had met while campaigning, all endeavouring in different ways to improve their own lives and to serve their country.
It wasn't just the struggles of these men and women that had moved me. Rather, it was their determination, their self-reliance, a relentless optimism in the face of hardship. It brought to mind a phrase that my pastor, Rev. Jeremiah A. Wright Jr.' had once used in a sermon. The audacity of hope ... It was that audacity, I thought, that joined...

answer the following question:

Who went into politics soon after Dreams of My Father was published? 

Obama