Given a document, find the main entity about whom the author is writing. Write the full name if mentioned in the text. Note that URLs in the text have been replaced with [Link].

Q: Sen. Bob Corker (R-TN)  speaks with reporters after announcing  his  retirement at the conclusion of  his  term on Capitol Hill in Washington  U.S.  September 26  2017. REUTERS/Aaron P. Bernstein
WASHINGTON (Reuters)  - U.S. Senator Bob Corker   the influential Republican chairman of the Senate Foreign Relations Committee  said on Tuesday he will not run for re-election  a blow to a party already struggling to balance divisions between mainstream and more populist wings.
An establishment Republican   Corker  has been criticized from the right  and a conservative activist had already announced a primary challenge. But he was expected to keep the seat  and had amassed a $7.5 million campaign war chest.
 Corker  has ruled out running for governor of Tennessee.
âI have no idea what Iâm going to do. No idea whatsoever â  Corker  said in an interview. But he said he was not leaving out of frustration over deep party divides that have often paralyzed Congress.
 Corker  announced  his  retirement on the day of the failure of the latest Republican effort to repeal former Democratic President Barack Obamaâs healthcare law.
âI am not going to be one of the people who leaves here badmouthing what is one of the greatest privileges of oneâs life â  Corker  said.
He said he realized he was ready to retire on Aug. 24 during a factory groundbreaking in Clarksville  Tennessee  and almost announced his decision at least twice before Tuesday.  Corker  said that he made his announcement now to allow a strong candidate time to enter the Senate race.
 Corker  is the first senator to announce  his  retirement ahead of the 2018 mid-term elections  when one-third of the 100-seat chamber will be up for grabs. Tennessee is a solidly Republican state and the party  which currently holds a 52-seat majority in the Senate  is favored to keep his seat.
In his official announcement   Corker  said that âafter much thought  consideration and family discussionâ over the past year  he and his wife Elizabeth âhave decided that I will leave the United States Senate when my term expires at the end of 2018.â
 Sen. Bob Corker (R-TN)  walks away after speaking with reporters after announcing  his  retirement at the conclusion of  his  term on Capitol Hill in Washington  U.S.  September 26  2017. REUTERS/Aaron P. Bernstein
CLASHES WITH  TRUMP
In August  after Trumpâs much-criticized reaction to violence at a white supremacist rally in Virginia   Corker  told reporters in  his  home state Tennessee that Trump had not been able to demonstrate the âstabilityâ or competence that  he  needed to be successful as president.
After the exchange  the two men had an hour-long meeting at the White House this month that  Corker  has described as a wide-ranging and friendly discussion.
 Corker  will remain chairman of the Foreign Relations Committee until he leaves in January 2019. He said he wanted the panel to address issues including Secretary of State Rex Tillersonâs State Department reorganization  food aid reform  and the fight against human trafficking and modern slavery.
 Corker  said the committee would address the international nuclear agreement with Iran  as Trump faces a mid-October deadline for deciding whether to certify that Tehran is complying with that pact. That decision could force Congress to decide whether to reimpose sanctions.  Corker  would not say whether Trump had decided to certify or not.

A: Bob Corker
****
Q: Gov. Jerry Brown of California  echoed those comments.
"In the United States  we have a federal system  and states have real power as do cities. And when cities and states combine together  and then join with powerful corporations  that's how we get stuff done "  he  said.
 His  speech was briefly interrupted by anti-coal and anti-fracking protesters  who held up banners and shouted "We're still in! Trump's still out!"
 California Governor Jerry Brown  speaks in the U.S. Climate Action Center at the COP 23 Fiji UN Climate Change Conference in Bonn  Germany  Saturday  Nov. 11  2017.  Brown 's and Michael Bloomberg's "America's Pledge" campaign works to compile and tally the climate actions of states  cities  colleges  businesses  and other local actors across the entire U.S. economy. (AP Photo/Martin Meissner)
 California Governor Jerry Brown  speaks in the U.S. Climate Action Center at the COP 23 Fiji UN Climate Change Conference in Bonn  Germany  Saturday  Nov. 11  2017.  Brown 's and Michael Bloomberg's "America's Pledge" campaign works to compile and tally the climate actions of states  cities  colleges  businesses  and other local actors across the entire U.S. economy. (AP Photo/Martin Meissner)

A: Jerry Brown
****
Q: Biden encourages Romney to run for Senate . 
Park City , Utah -LRB- CNN -RRB- Former Vice President Joe Biden is encouraging onetime rival Mitt Romney to return to public life and run for Senate . 
Biden spoke at Romney 's ideas summit , an annual gathering of donors and business leaders in Utah . 
During a private event Friday night in Park City , Biden called Romney a man of integrity and said he should mount a challenge next year , according to two people in the room . 
The comment was quick and off-hand , but the crowd of Romney loyalists appreciated it and applauded . 
Romney , a former Massachusetts governor , is a Mormon and owns a home in Utah . 
The two men were on opposite sides of the 2012 election -- Biden as the running mate of President Barack Obama and Romney as the Republican presidential nominee . 
Romney and Biden both considered running for president last year , but both deferred to candidates they saw as having an overwhelming financial advantage -LRB- Jeb Bush on the Republican side ; Hillary Clinton on the Democratic side -RRB- . 
Romney , 70 , has not stayed far from politics , either . 
After being passed over for Trump 's secretary of state , Romney has campaigned for GOP candidates and weighed in on political matters via social media . 
Speculation has grown that Romney could run for the Senate in Utah .

A:
Mitt Romney
****