Use an ActionChain with key_down to press the control key, and key_up to release it:
import time
from selenium import webdriver
from selenium.webdriver.common.action_chains import ActionChains
from selenium.webdriver.common.keys import Keys
driver = webdriver.Chrome()
driver.get('http://google.com')
element = driver.find_element_by_link_text('About')
ActionChains(driver) \
.key_down(Keys.CONTROL) \
.click(element) \
.key_up(Keys.CONTROL) \
.perform()
time.sleep(10) # Pause to allow you to inspect the browser.
driver.quit()